We usually stain Fontana Masson on formalin fixed and paraffin embedded
tissue. So there is also an alcoholstep because of dehydration. Melanocytes
are stained well and show black pigment.
You have to use neutral buffered formaldehyd, because without buffering
formalinpigment may occur, that has also reducing activity on the
silversolution.
If all melanin in the tissue is stained or if there is a remaining unstained
part is beyound my knowledge.

hope this helps
Gudrun



-----Ursprüngliche Nachricht-----
Von: histonet-bounces@lists.utsouthwestern.edu
[mailto:histonet-bounces@lists.utsouthwestern.edu] Im Auftrag von Randy Khoo
Gesendet: Freitag, 08. September 2006 03:47
An: histonet@lists.utsouthwestern.edu
Betreff: [Histonet] Fontana Masson Staining

Dear All,

I hope someone can help me out here. I read that alcohol will dissolve the
argentaffin granules. How does the chemistry work here? Is it only because
of beta-carboline formation or are there other reactions taking place as
well? Is the disappearance of argentaffin granules under alcohol fixation
confirmatory of its presence if compared to a parallel formaldehyde staining
showing its presence?

Also, if I use alcohol fixation, the cells tend to shrink and shrivel. Is
there any way I can preserve the morphology with alcohol fixation (ie any
other components I can add to alcohol)?

Does Fontana-Masson staining pick up oxidized melanin?
I presume its ability to reduce silver ions is because in the natural state,
melanin is mostly in the reduced form.

Therefore, is it possible that FM is not picking up all the melanin in a
cell? However, am I right in assuming that formalin as a strong reducing
agent would reduce all the melanin in melancytes if they are fixed in
formalin?

Thanks in advance.

Randy






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